Mill – Tooling – Clamps and Part Holders

Like all tooling, holding a part to be worked on securely is a practiced art.  I’ve seen large industrial CNC machines that you could basically throw a part at it and it would grab it and orient it so it could be worked on at any angle necessary.  But in the world real world however, you have to plan how to hold your part with as much care as how to cut it.  Sometimes (though rarely) it’s just a matter of slapping it in a vise, but usually, it involves some creative clamping to assure the part is immovable and accessible for the operation.  Sometimes, that’s a royal pain in the neck!

Again, the secret lies in versatility.  You need to have a broad enough variety to tools available so you don’t have to stop and go buy something every time you turn around.  And a lot of times that involves making a fixture.

A fixture is a specialized contraption that holds a part for a particular purpose; sometimes that’s a whole set of operations and/or for accurate assembly.  But an experienced machinist is frequently (by definition) an expert tool-maker as well.

Sometimes parts need to be designed to allow interim tooling features, like tooling mount-holes or tabs.  You just have to think outside the box – or the finished part as the case may be.  For example, I’ve seen huge fragile parts that are completely free of mounting features, because they were created in the original operations and used throughout the entire process, and then removed at the very end.  Likewise, I’ve made parts that there was no good way to grab onto its stock or finished surfaces, so the first operation was to drill a couple holes in a position that would eventually be pocketed out, and bolt the whole thing onto a fixture that I could hold onto properly, and then do most of the operations, and then finally I reached a point where there were finished surfaces I could grab onto to finish the rest of the details.

A Rotary Table is a general purpose fixture that is quite handy as-is on the mill.  But like the mill table, you have options on how to actually hold the part; wither by clamping or in some kind of chuck or vise. 

A chuck, which you might normally associate with a Lathe, is great for holding a round stock for operations on the axis of the part, unless you are using it on a Rotary Table, which is also used for operations perpendicular to the axis of the part.

A vise is great for working on one of the axis of a rectangular stock.

Clamps are for everything else.  Sometimes it requires brute force to grab onto awkward shapes or for awkward orientations; and clamps are the last resort.

In practice however, mounting parts is usually a combination of resources and hardware.  Like the machine itself, mounting a part securely is vitally important to the overall success of the operations to assure clean and accurate features.